1. Field of the Invention
This invention relates to a constituent unit for an optical information processing system. More particularly the present invention relates to an optical information processing system wherein light is utilized as a medium for carrying information and a constituent unit group for such an optical information processing system. This invention also relates to an optical information processing system which utilizes the constituent unit or the constituent unit group.
2. Description of the Prior Art
A typical approach in the fields of optical computing and optical information processing is to carry out large-scaled parallel processing on two-dimensional patterns by utilizing the characteristics that the light can travel quickly and can be processed in parallel. In such cases, predetermined optical parallel processing is often carried out by simultaneously forming multiple images from an input pattern and carrying out a different image operation on each of the multiple images. Examples of such processing include parallel operations for calculating the sum of products of a matrix and a vector, which operations form the foundation of a neural network, and parallel operations for calculating the levels of correlation between an input image and comparative images in pattern recognition. By way of example, a multiple imaging optical system shown in FIG. 18 is one of basic components in optical parallel processing.
Various multiple imaging optical systems have heretofore been proposed with respect both incoherent illumination and coherent illumination. For the processing under incoherent illumination, the image forming performance is rated with respect to a multiple imaging optical system which utilizes a lens array. For the processing under coherent illumination, various devices, such as a Dammann grating, a two-dimensional phase grating, a hologram device, and a pinhole array self-imaging device, have heretofore been proposed. The multiple imaging optical systems are applied to parallel operations for calculating the sum of products of a matrix and a vector, parallel optical connection utilizing the operations for calculating the sum of products of a matrix and a vector, parallel matched filtering, and the like.
Also, application of a multiple imaging optical system, which utilizes a microlens array, to optical parallel processing has been proposed by Hamanaka, et al. in "Parallel Processing Using Microlens Arrays," MICROOPTICS NEWS, Bulletin of Microoptics Research Group, 1991.5.31, Vol. 9, No. 2, pp. 59-64. However, the system for the optical parallel processing has the drawbacks in that the alignment of the parts of the system must be adjusted accurately, and the system is difficult to assemble and adjust. Also, an optical information transmitter shown in FIG. 19 has been proposed in Japanese Unexamined Patent Publication No. 4(1992)-125517. As illustrated in FIG. 19, the proposed optical information transmitter comprises a rod lens 108 and a plate microlens array (hereinafter referred to as PML) 109, which are adhered and secured to each other and constitute a multiple imaging optical system. A transmission type of spatial light modulator (hereinafter referred to as SLM) 110, which displays an input image, is located on the front surface of the multiple imaging optical system, (i.e. on the light entry surface of the rod lens 108) such that the SLM 110 may be in close contact with and secured to the light entry surface of the rod lens 108. Also, an incoherent illumination device 111 (e.g. a packaged LED array) is located at the back of the SLM 110 such that the incoherent illumination device 111 may be in close contact with and secured to the SLM 110.
A reference pattern array 106 is located on a light radiating surface of the PML 109 such that the reference pattern array 106 may be in close contact with and secured to the light radiating surface of the PML 109. Further, a detector array 107 is located at the back of the reference pattern array 106 such that the detector array 107 may be in close contact with and secured to the reference pattern array 106.
With the optical system described above, the adjustment and fixing of the alignment of the optical system, which were very difficult to carry out, can be achieved very easily.
Also, with the optical system described above, for example, in cases where a character image is displayed on the SLM 110 and patterns of reference characters are formed on the reference pattern array 106, comparison signals representing the results of comparison between the input character image and the plurality of the patterns of the reference characters can be detected simultaneously and in parallel by the detector array 107. In cases where the input image is a vector and a matrix is formed on the reference pattern array 106, the results of the operations for calculating the sum of products of the vector and the matrix can be detected by the detector array 107.
However, with the multiple imaging optical system described above, the input image displayed over the entire region of the SLM 110 must be totally connected such that it may be fed into every small region on the detector array 107. Therefore, the distance between the arrays, such as the lens array, which constitute the optical system, must be comparatively long. Accordingly, even if the optical system described above can process the information representing two-dimensional patterns by utilizing the characteristics that the light can travel quickly and can be processed in parallel, the optical system described above cannot be kept small in size.